Gary Neville told Sky Sports News that Manchester United MUST not sell Wayne Rooney to title rivals Chelsea.
The Stamford Bridge side have seen two bids for Rooney rejected by the Old Trafford hierarchy, but the 27-year-old is reportedly set to submit a formal transfer request in an attempt to engineer a move.
Sky Sports pundit and former United full-back Neville reckons David Moyes' team need to keep a man that will play an instrumental role in their pursuit of a 21st top-flight crown and second in row.
But he says that if Rooney does depart then Moyes - who officially succeeded Sir Alex Ferguson in the Old Trafford hot-seat on July 1 - must draft in a "major, major" replacement.
Neville said: "Manchester United cannot sell Wayne Rooney to Chelsea Football Club - unless they bring in a major, major signing like Gareth Bale or Cristiano Ronaldo.
"You have absolute gold in Rooney, someone who is proven over six, seven, eight years; who delivers season in, season out; and is one of the top goals and assists man in the league consistently - even last season when he wasn't at his strongest.
"He will work his backside off and never drop his level in training and the importance of Rooney [is huge]; he is a vital player, a champion player and someone that wins you the league.
"He is the guy who in the middle of October when you are four points behind in the league, going to Chelsea and have Arsenal the week after, sits in front of his midfield two, works his backside off, gets up the pitch, gets back, sets up goals and digs in.
"Don't underestimate the value of Rooney to Manchester United's success over the last eight years and the way he is liked amongst his team-mates.
"Manchester United do not need to sell him for the money and I don't think they will sell him at all - and if they do, not until they bring in a decent replacement."
Manchester United poached the Premier League title from local rivals Manchester City last term, but the Citizens have responded by appointing Manuel Pellegrini as manager and splashing the clash on the likes of Stevan Jovetic and Alvaro Negredo.
Neville, though, believes City's established stars will be key in their bid to regain top-flight silverware.
"City have done their business but I still think their best players are [Joe] Hart, [Vincent] Kompany, [Yaya] Toure and [Sergio] Aguero, and getting performances out of those four is the most critical thing," said Neville.
"Fernandinho will be a great addition, as at times there was great expectation on Toure, but the spine of the team - you've also got [David] Silva and Matija Nastasic - have to be at their best.
"The rest are just side dishes; they are good side dishes but they have to prove themselves in the Premier League, and the ones that are still there are the ones that will win them the league."